an "ideal" scuba tank

[spectrum]

An almost 8# swing in buoyancy from full to empty One of the reasons I switched from aluminum to steel.

The swing has nothing to do with material, it's strictly the depletion of the contents.

 

[spectrum]

There is a carbon fiber tank made by luxfer i think that is rated and ment for scuba

Expensive but light purpose built for scuba probably the wave of tomorrow today but its ahead of its time most shops cant fill that high plus most arent trained to vip them.

L6X® Hoop-wrap cylinder specifications - Luxfer: Setting The Standard Worldwide

It's a wrapped aluminum, cylinder. The pressure goes up a notch (if you can get it) and the lifespan is limited. Beside all that it's expensive.

 

[50Fathom]

An almost 8# swing in buoyancy from full to empty One of the reasons I switched from aluminum to steel.

Seems to me that that's a fixed swing, since it's the weight of 100cf of gas (likely air).

100cf gas weight swing is the same whether it's steels or aluminums.

Hell, the Worthington HP100s swing 8 pounds. -10 to -2.

Now, for drysuit diving I agree, I want the tank to stay negative, but unless you're diving a REALLY hypoxic trimix, (10/70 or 6/80 or something else for insane depths), then the gas swing with larger capacity tanks is gonna be big.

 

[50Fathom]

The swing has noting to do with material, it's strictly the depletion of the contents.

You got to it before I did, and were more succinct.

My philosophy is, "Why use four words when 12 will do?"

 

[scubamarketing]

You got to it before I did, and were more succinct.

My philosophy is, "Why use four words when 12 will do?"

Okay, sorry, jump all over me

I meant a swing to being positive. I do dive dry, so steel has some great advantages.

 

[50Fathom]

Okay, sorry, jump all over me

I meant a swing to being positive. I do dive dry, so steel has some great advantages.

No jumping involved and not to attack.

I'm with you in that I MUCH prefer the buoyancy characteristics of steels, but big swings are usually from big gas capacities, that's all I was saying.

Aluminums are NOT my favorite tank by FAR, but they are the most common, by FAR, so I dive them and deal with it.

I'm lucky in that my shop has a huge fleet of old Steel 72s, which have arguably the perfect buoyancy of any tank, (4-5 pounds negative full, perfectly neutral empty), so I use them every chance I get. Which is often, since the shop owner likes to see students in aluminums, so the DMs and instructors are often in steels since that's all that's leftover.

God, I love steel tanks.

 

[sam1]

(Put another way, "good" tank weight reduces positive buoyancy; "bad" tank weight does not. My HP80s have 24.9 pounds of "good" weight and (only) 2.8 pounds of "bad" weight.)

Eureka! I've figured it out! I wanted to understand what determines what I have called "bad" tank weight—i.e., weight beyond that needed to offset the buoyancy of the water displaced by the (internal) capacity of the cylinder. [I know, some (many?) of you are thinking, why doesn’t he stop thinking about such arcane issues and just dive! Well, I am not in a position to dive as much as I’d like and when I can’t dive I think about it!] “Bad” weight is equal to the weight of the water displaced by the tank material itself (i.e., the density of water multiplied by the difference between the external tank volume and the internal tank volume). As is well known, because of the properties of aluminum, the walls of aluminum tanks need to be thicker than steel tanks (with the same working pressure).

Some numbers (calculated from tank specs from http://www.huronscuba.com/equipment/scubaCylinderSpecification.html) :

Luxfer AL80: External Tank Volume = 15.86 liters; Internal Tank Volume=10.76 liters; thus Volume of Tank Material = 5.10 liters. Using a density of salt water of 1.025 kilograms/liter yields “bad” tank weight of 5.23 kg=11.5 pounds.

Worthington HP80: External Tank Volume = 10.95 liters; Internal Tank Volume=9.69 liters; thus Volume of Tank Material = 1.26 liters. Using a density of salt water of 1.025 kilograms/liter yields “bad” tank weight of 1.29 kg=2.8 pounds.

 

[The Kraken]

HP100. Shorter than an AL 80. Lighter than an AL 80. 100 cu. ft. of gas. Negatively buoyant.

Nuff said.

the K

 

[BuoyantC]

For warm salt water, an AL80 works perfectly for me. When you get to cold water, I love my HP80. 80 cf is plenty for my style of diving so the 100's are just unnecessarily big. We see a lot of AL C80's here that are a few more lbs negative, but it's just a trade off with weight on a belt. I prefer the S80 for that reason.

But that's just me.

 

[Teljkon]

It's a wrapped aluminum, cylinder. The pressure goes up a notch (if you can get it) and the lifespan is limited. Beside all that it's expensive.

Not an endorsment just saying it is out there. By no means should everyone run out and buy them. How ever if your looking for a lighter cary wieght for humping your tanks to your dive site could be nice.